socket wrench

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A wrench having interchangeable sockets to fit over nuts and bolts of different sizes.

from The Century Dictionary.

• noun A wrench for turning nuts, having a socket fitted to a special size and shape of nut to be turned. See cut under wrench.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A type of wrench featuring multiple interchangeable socket heads (each designed to fit a particular size of bolt head or other fastener) which can be attached by a socket arrangement to a ratcheting wrench handle or other driver.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a wrench with a handle onto which sockets of different sizes can be fitted